A dialysis machine in a conventional blood purification apparatus, as shown in FIG. 3, includes a blood circuit 100, a dialyzer 103, a blood pump 104, an arterial drip chamber 105, a venous drip chamber 106, an overflow line L2, and a dialysis device 108. The blood circuit 100 is provided with an arterial blood circuit 101 having an arterial needle a, and a venous blood circuit 102 having a venous needle b. The dialyzer 103 is provided between the arterial blood circuit 101 and the venous blood circuit 102, and purifies blood of a patient, flowing in the blood circuit 100. The arterial blood circuit 101 is provided with the blood pump 104. The arterial blood circuit 101 and the venous blood circuit 102 are each provided with the arterial drip chamber 105 and the venous drip chamber 106, respectively. The overflow line L2 is provided at an air-layer side of the venous drip chamber 105 and extended therefrom. The dialysis device 108 is capable of supplying dialysate to the dialyzer 103.
In addition, a saline solution bag 107 is connected to a portion of the arterial blood circuit 101 between the arterial needle a and the blood pump 104, and supplied with a priming solution (e.g., a saline solution) through a saline line L1 so as to perform priming prior to a dialysis treatment and supply an additional priming solution during the dialysis treatment. For example, when washing and priming are performed, an end of the arterial blood circuit 101 and an end of the venous blood circuit 102 are connected to each other before connecting each of the circuits 101 and 102 to the arterial needle a and the venous needle b, respectively. Subsequently, by turning on the blood pump 104, the blood circuit 100 is filled with the priming solution while discharging the priming solution from the overflow line L2.
To start the dialysis treatment, each of the arterial needle a and the venous needle b connected to each of the ends of the arterial blood circuit 101 and the venous blood circuit 102, respectively, is inserted into the patient. Then, by turning on the blood pump 104 while supplying the dialysate from the dialysis device 108 to the dialyzer 103, the blood of the patient is introduced to the blood circuit 100 through the arterial needle a to purify and remove water through the dialyzer 103, and returned to the patient through the venous needle b.
At the time the dialysis treatment is started, a large amount of the priming solution pre-filled in the blood circuit 100 is to be prevented from being introduced into the body of the patient through the venous needle b. Thus, conventionally, electromagnetic valves V1 and V2 are firstly set to closed and open positions, respectively, and switched to open and closed positions, respectively, when it is visually confirmed that the priming solution in a portion of the venous blood circuit 102 near the venous needle b is replaced with the blood.
Thus, by switching the positions of the electromagnetic valves V1 and V2, the priming solution is discharged from the overflow line L2 prior to being replaced with the blood in the portion of the venous blood circuit 102 near the venous needle b, and the blood is returned to the body of the patient through the venous blood needle b after replacing the priming solution. For example, the above-described conventional blood purification apparatus, which discharges the priming solution from the overflow line L2 and replaces the priming solution with the blood, is described in the Japanese Laid-Open Patent Publication 2002-325837.
However, when using such conventional blood purification apparatus, because the electromagnetic valves V1 and V2 are manually switched in positions after a medical staff (e.g., a medical doctor) visually confirms that the priming solution in the portion of the venous blood circuit 102 near the venous needle b is replaced with the blood, the medical staff has to carefully monitor that portion of the venous blood circuit 102 at the time the dialysis treatment is started, making the dialysis treatment inefficient. Also, if the electromagnetic valves V1 and V2 are switched in positions too early, a large amount of the priming solution is introduced to the body of the patient. On the other hand, if switched too late, the patient's blood circulated extracorporeally is discharged from the overflow line L2.